The purpose of this study is to determine the effect of malpractice on the productivity of obstetricians and gynecologists (OBG's). Physicians report engaging in practice alterations to alter the patient's perception of care and reduce the probability of being found negligent should litigation occur. Such alterations consist of keeping more extensive records, defensively monitoring journals, spending more time with patients, and delegating less to allied health personnel. The main hypothesis of this research is that these practice alterations result in a decrease in productivity when output is defined as visits, an accepted measure of output in the physician services literature. Also, it is posited that the effect is greater for group practice than solo practices because of increased peer review in group practices. This productivity effect will be measured by the estimation of a system of equations in which a transcendental exponential production function is determined simultaneously with claims frequency and severity. Tort reforms are determined simultaneously with both the frequency and severity of claims and the cesarean section rate. The malpractice environment is evaluated at the level of the Insurance Services Office rating territory, which provides a relatively homogeneous environment. Negative coefficients are expected for the malpractice variables in the output equation, with larger negative coefficients expected for groups. The population from which the sample will be drawn consists of 16,562 Fellows of the American College of Obstetricians and Gynecologists (ACOG) practicing in the 12 mo populous states. About 62% of office based OBG's and 59% of the civilian population a located in these states. A disproportionate stratified random sample of 5,000 Fellows will be drawn from ACOG's membership records, with 200 surveys sent to OBG's in each o the 25 territories in these states. Assuming a 50% response rate, the maximum sampling error would be only 1.96% overall at a 95% confidence level. This study will be useful to policymakers concerned with the indirect costs associated with malpractice which are affecting the affordability and availability of prenatal care. Additionally, since projections of physician supply are sensitive to t level of productivity assumed, a better understanding of the determinants of productivity will be useful in formulating policies that affect the supply of physicians.